Some update.

include/Basic/SourceCode.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <Basic/Location.h>
+#include <clang/Basic/SourceLocation.h>
+
+namespace clice {
+
+/// Convert a clang::SourceLocation to a proto::Position according to the
+/// specified encoding kind. Note that `SourceLocation` in clang is one-based and
+/// is always encoded in UTF-8.
+proto::Position toPosition(llvm::StringRef content,
+                           clang::SourceLocation location,
+                           proto::PositionEncodingKind kind,
+                           const clang::SourceManager& srcMgr);
+
+/// Same as above, but for a group of locations. It is more efficient than calling
+/// `toLocation` multiple times. Note that the locations must be sorted.
+std::vector<proto::Position> toPosition(llvm::StringRef content,
+                                        llvm::ArrayRef<clang::SourceLocation> locations,
+                                        proto::PositionEncodingKind kind,
+                                        const clang::SourceManager& srcMgr);
+
+/// Convert a proto::Position to a clang::SourceLocation according to the
+/// specified encoding kind. If any error occurs, return an invalid location.
+clang::SourceLocation toSourceLocation(llvm::StringRef content,
+                                       proto::Position position,
+                                       proto::PositionEncodingKind kind,
+                                       const clang::SourceManager& srcMgr);
+
+}  // namespace clice